Hybrid dispersions made of polyadducts and radical polymers

ABSTRACT

Hybrid dispersions comprising polyadducts and free-radical addition polymers, obtainable by first emulsifying the constituent monomers of said polyadducts and polymers in water and then conducting the polyaddition to prepare the polyadducts and the free-radical addition polymerization to prepare the polymers, the respective monomers being emulsified in water before 40% of the monomers of which the polyadducts are composed have reacted to form such polyadducts.

The present invention relates to hybrid dispersions comprisingpolyadducts and free-radical addition polymers, obtainable by firstemulsifying the constituent monomers of said polyadducts and polymers inwater and then conducting the polyaddition to prepare the polyadductsand the free-radical addition polymerization to prepare the polymers,the respective monomers being emulsified in water before 40% of themonomers of which the polyadducts are composed have reacted to form suchpolyadducts.

The present invention further relates to a process for preparing thehybrid dispersions of the invention and also to their use as binders forcoating compositions or impregnating compositions, in adhesives,varnishes, paints or paper coating slips or as binders for fiber webs.

Hybrid dispersions comprising, for example, polyurethane dispersions andfree-radical addition polymers are already known in the art. Hybriddispersions of this kind are commonly prepared by starting from apolyurethane dispersion stabilized by incorporated ionic or nonionic,water-soluble groups and then conducting a free-radical additionpolymerization in the particles of said polyurethane dispersion.However, as a result of their complicated preparation process, in whichfirst a polyurethane is produced, this polyurethane is then emulsified,and then addition polymerization is carried out in the presence of thesecondary dispersion obtained by emulsification, these hybriddispersions are very expensive. Moreover, they have a permanenthydrophilicity which makes polymer films obtained from them sensitive towater.

From the prior art it is also known that both free-radical additionpolymers (WO-A 00/29451) and polyadducts (WO-A 00/29465) can be preparedin aqueous miniemulsions.

Furthermore, WO-A 01/44334 describes using polyurethanes in aqueousminiemulsions which comprise polyacrylates. However, systems of thiskind have the drawback that they always require a multistage preparationprocess, in which first a polyadduct is prepared, this polyadduct isthen emulsified, and in the presence of the emulsified polyadduct,finally, a free-radical miniemulsion addition polymerization isconducted. In such hybrid dispersions, moreover, the monomer phase isfound to have an unfavorably heightened viscosity in the presence of thepolyadducts, which give rise, inter alia, to a relatively wide particlesize distribution and relatively large emulsion droplets when emulsionis carried out, for example, with ultrasound. Additionally, the choiceof adducts is limited to linear, soluble materials; crosslinked polymerscannot be employed. Moreover, the yield of polyadducts is limited.

It is an object of the present invention to remedy the disadvantagesdepicted and to provide improved hybrid dispersions which possess aparticle distribution which is not too wide, which are able to include avery large number of different adducts, which are also obtained in arelatively high yield, and which are obtainable by a relatively simpleprocess.

We have found that this object is achieved by the hybrid dispersionsdefined at the outset. The present invention additionally extends to theprocess for preparing hybrid dispersions and to their use as binders,for coating compositions or impregnations inter alia.

The hybrid dispersions of the invention comprising polyadducts andfree-radical addition polymers are obtainable by first emulsifying theconstituent monomers of the said polyadducts and said polymers in water,i.e., introducing the respective monomers into an aqueous dispersion bymeans of customary emulsifiers.

This is followed by the actual polyaddition for preparing thepolyadducts and the actual free-radical addition polymerization forpreparing the polymers. Another feature of the hybrid dispersions of theinvention is that the particular monomers required are emulsified inwater before 40% of the monomers of which the polyadducts are composedhave reacted to form such polyadducts. Preferably, the monomers requiredin each case to prepare the polyadducts and the polymers should alreadybe emulsified in water before 30%, advisably 20%, more advisably 10%, inparticular 5%, and with particular preference 1% of the monomers ofwhich the polyadducts are composed have reacted to form suchpolyadducts.

Suitable polyadducts are all those polymers which can be obtained by acorresponding polyaddition reaction. They include polyurethanes, whichare obtainable by reacting polyisocyanates with compounds containingisocyanate-reactive groups.

In the case of the polyurethanes, the ratio of their constituentmonomers, i.e., essentially the polyisocyanates and the compoundscontaining isocyanate-reactive groups, is situated in a range such thatthe ratio of isocyanate groups (a) to isocyanate-reactive groups (b) isfrom 0.5:1 to 5:1, in particular from 0.8:1 to 3:1, preferably from0.9:1 to 1.5:1, and with particular preference 1:1.

Suitable polyisocyanates preferably include the diisocyanates commonlyused in polyurethane chemistry.

Mention may be made in particular of diisocyanates X(NCO)₂, where X isan aliphatic hydrocarbon radical having 4 to 12 carbon atoms, acycloaliphatic or aromatic hydrocarbon radical having 6 to 15 carbonatoms or an araliphatic hydrocarbon radical having 7 to 15 carbon atoms.Examples of such diisocyanates are tetramethylene diisocyanate,hexamethylene diisocyanate, dodecamethylene diisocyanate,1,4-diisocyanatocyclohexane,1-isocyanato-3,5,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI),2,2-bis(4-isocyanatocyclohexyl)propane, trimethylhexane diisocyanate,1,4-diisocyanatobenzene, 2,4-diisocyanatotoluene,2,6-diisocyanatotoluene, 4,4′-diisocyanatodiphenylmethane,2,4′-diisocyanatodiphenylmethane, p-xylylene diisocyanate,tetramethylxylylene diisocyanate (TMXDI), the isomers ofbis(4-isocyanatocyclohexyl)methane (HMDI) such as the trans/trans, thecis/cis and the cis/transisomer, and mixtures of these compounds.Sterically hindered diisocyanates are particularly advantageous in thiscontext.

Further suitable polyisocyanates include nonane triisocyanate and lysinetriisocyanate, and also the biurets of the common diisocyanates.

Significant mixtures of these diisocyanates include the mixtures of therespective structural isomers of diisocyanatotoluene anddiisocyanatodiphenylmethane; particular suitability is possessed by themixture of 80 mol % of 2,4-diisocyanatotoluene and 20 mol % of2,6-diisocyanatotoluene. It is additionally possible to use the mixturesof aromatic isocyanates with aliphatic or cycloaliphatic isocyanates,the preferred ratio of aliphatic to aromatic isocyanates being from 4:1to 1:4.

As compounds (a) it is also possible to use isocyanates which inaddition to the free isocyanate groups carry further, blocked isocyanategroups, e.g., isocyanurate, biuret, urea, allophanate, uretdione orcarbodiimide groups.

Examples of suitable isocyanate-reactive groups are hydroxyl, epoxy,thiol, and primary and secondary amino groups. Preference is given tousing hydroxyl-containing compounds or monomers (b).

In addition it is also possible to use amino-containing compounds ormonomers (b3).

Preferred compounds or monomers (b) used are diols.

For effective film formation and elasticity, suitable compounds (b)containing isocyanate-reactive groups are principally diols (b1) ofrelatively high molecular weight, having a molecular weight of fromabout 500 to 5000, preferably from about 1000 to 3000, g/mol.

The diols (b1) comprise, in particular, polyesterpolyols, which areknown, for example, from Ullmanns Encyklopädie der technischen Chemie,4th edition, volume 19, pp. 62-65. It is preferred to usepolyesterpolyols obtained by reacting dihydric alcohols with dibasiccarboxylic acids. Instead of the free polycarboxylic acids it is alsopossible to use the corresponding polycarboxylic anhydrides orcorresponding polycarboxylic esters with lower alcohols, or mixturesthereof, to prepare the polyesterpolyols. The polycarboxylic acids maybe aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic andmay where appropriate be unsaturated and/or substituted, by halogenatoms for example. Examples thereof that may be mentioned include thefollowing: suberic acid, azelaic acid, phthalic acid, isophthalic acid,phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalicanhydride, tetrachlorophthalic anhydride,endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleicacid, maleic anhydride, alkenylsuccinic acid, fumaric acid, and dimericfatty acids. Preference is given to dicarboxylic acids of the formulaHOOC—(CH₂)_(y)—COOH, where y is a number from 1 to 20, preferably aneven number from 2 to 20, examples thereof being succinic acid, adipicacid, dodecanedicarboxylic acid, and sebacic acid.

Suitable diols further include tricyclodecanedimethanol[3(4),8(9)-bis(hydroxymethyl)tricyclo[5.2.1]decane] and also Dianols(ethoxylated bisphenol A glycidyl ethers).

Examples of suitable diols include ethylene glycol, propane-1,2-diol,propane-1,3-diol, butane-1,3-diol, butane-1,4-diol, butene-1,4-diol,butyne-1,4-diol, pentane-1,5-diol, neopentyl glycol,bis(hydroxymethyl)cyclohexanes such as1,4-bis(hydroxymethyl)cyclohexane, 2-methylpropane-1,3-diol,methylpentanediols, diethylene glycol, triethylene glycol, tetraethyleneglycol, polyethylene glycol, dipropylene glycol, polypropylene glycol,dibutylene glycol, and polybutylene glycols. Preference is given toalcohols of the formula HO—(CH₂)_(x)—OH, where x is a number from 1 to20, preferably an even number from 2 to 20. Examples thereof areethylene glycol, butane-1,4-diol, hexane-1,6-diol, octane-1,8-diol, anddodecane-1,12-diol. Preference is further given to neopentyl glycol andpentane-1,5-diol. These diols may also be used as diols (b2) directly tosynthesize the polyurethanes.

Also suitable, furthermore, are polycarbonatediols (b1), as may beobtained, for example, by reacting phosgene with an excess of the lowmolecular weight alcohols specified as synthesis components for thepolyesterpolyols.

Also suitable are lactone-based polyesterdiols (b1), which arehomopolymers or copolymers of lactones, preferably hydroxy-terminaladducts of lactones with suitable difunctional starter molecules.Suitable lactones include preferably those derived from compounds of theformula HO—(CH₂)_(z)—COOH, where z is a number from 1 to 20 and whereone hydrogen atom of a methylene unit may also be substituted by a C₁ toC₄ alkyl radical. Examples are epsilon-caprolactone, β-propiolactone,γ-butyrolactone and/or methyl-epsilon-caprolactone, and also mixturesthereof. Examples of suitable starter components are the low molecularweight dihydric alcohols specified above as synthesis components for thepolyesterpolyols. The corresponding polymers of ε-caprolactone areparticularly preferred. Lower polyesterdiols or polyetherdiols may alsobe used as starters for preparing the lactone polymers. Instead of thepolymers of lactones it is also possible to use the corresponding,chemically equivalent polycondensates of the hydroxycarboxylic acidscorresponding to the lactones.

Further suitable monomers (b1) include polyetherdiols. These areobtainable in particular by polymerizing ethylene oxide, propyleneoxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrinwith itself, in the presence of BF₃, for example, or by addition ofthese compounds, where appropriate as a mixture or in succession, withstarting components containing reactive hydrogen atoms, such as alcoholsor amines, e.g., water, ethylene glycol, propane-1,2-diol,1,2-bis(4-hydroxyphenyl)propane or aniline. Particular preference isgiven to polytetrahydrofuran with a molecular weight of from 240 to5000, in particular from 500 to 4500.

Likewise suitable are polyhydroxyolefins (b1), preferably those having 2terminal hydroxyl groups, e.g., α,ω-dihydroxypolybutadiene,α,ω-dihydroxypolymethacrylic esters or α,ω-dihydroxypolyacrylic esters,as monomers (b1). Such compounds are known, for example, from EP-A-0 622378. Further suitable polyols (b1) are polyacetals, polysiloxanes, andalkyd resins.

Instead of the diols (b1) it is also possible in principle to use lowmolecular weight isocyanate-reactive compounds, having a molecularweight of from 62 to 500, in particular 62 to 200, g/mol. It ispreferred to use low molecular weight diols (b2).

Diols (b2) used are in particular short-chain alkanediols specified assynthesis components for the preparation of polyesterpolyols, preferencebeing given to the branched and unbranched diols having 2 to 20 carbonatoms and an even number of carbon atoms, and also pentane-1,5-diol.Also suitable as diols (b2) are phenols or bisphenol A or F.

The hardness and the modulus of elasticity of the polyurethanes can beincreased by using not only the diols (b1) but also the low molecularweight diols (b2) as diols (b).

The fraction of the diols (b1), based on the total amount of the diolsb, is preferably from 0 to 100, in particular from 10 to 100, withparticular preference from 20 to 100 mol % , and the fraction of themonomers (b2), based on the total amount of the diols (b), is from 0 to100, in particular from 0 to 90, with particular preference from 0 to 80mol % . With particular preference the molar ratio of the diols (b1) tothe monomers (b2) is from 1:0 to 0:1, more preferably from 1:0 to 1:10,with particular preference from 1:0 to 1:5.

For components (a) and (b) it is also possible to use functionalities>2.

Examples of suitable monomers (b3) are hydrazine, hydrazine hydrate,ethylenediamine, propylenediamine, diethylenetriamine,dipropylenetriamine, isophoronediamine, 1,4-cyclohexyldiamine, andpiperazine.

In minor amounts it is also possible to use monofunctionalhydroxyl-containing and/or amino-containing monomers. Their fractionshould not exceed 10 mol % of components (a) and (b). Furthermore, invery small fractions, the monomers used may also include ionic ornonionic hydrophilic compounds. Preferably, however, such monomers willbe avoided.

Further suitable polyadducts include the reaction products of epoxideswith, for example, alcohols, thiols, amines, acid anhydrides orcarboxylic acids, and also combinations thereof.

Particular mention may be made here of the reaction product of epoxyresins with alcohol compounds having two OH groups or with dicarboxylicacids.

Examples of suitable epoxide compounds include mono- and polyfunctionalglycidyl ethers.

In this context it is particularly preferred to use epoxide compoundswith a functionality of two or three, examples being the correspondingglycidyl ethers. Particularly suitable epoxide compounds includebisphenol A diglycidyl ethers of the formula (I)

where n is 0 to 15.

The corresponding bisphenol A diglycidyl ether derivative where n=0 issold, for example, as a commercial product under the name Epicote® 828by Shell.

Further particularly suitable epoxide compounds include butanedioldiglycidyl ether, pentaerythritol triglycidyl ether, neopentyl glycoldiglycidyl ether or hexanediol diglycidyl ether. It is also possible touse water-dispersible epoxide compounds.

Considered generally, epoxide compounds which can be used includearomatic glycidyl compounds such as the bisphenols A of the formula (I)or their bromine derivatives, and also phenol novolak glycidyl ether orcresol novolak glycidyl ether, bisphenol F diglycidyl ether,glyoxal-tetraphenol tetraglycidyl ether, N,N-diglycidylaniline,p-aminophenol triglycide or else 4,4′-diaminodiphenylmethanetetraglycide.

Further suitable epoxide compounds include cycloaliphatic glycidylcompounds such as, for example, diglycidyl tetrahydrophthalate,diglycidyl hexahydrophthalate or hydrogenated bisphenol A diglycidylethers, or heterocyclic glycidyl compounds such as triglycidylisocyanurate and also triglycidylbishydantoin.

As epoxide compounds it is additionally possible, furthermore, to usecycloaliphatic epoxy resins such as 3,4-epoxycyclohexylmethyl3′,4′-epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl)adipate or3-(3′,4′-epoxycyclohexyl)2,4-dioxaspiro[5,5]-8,9-epoxyundecane, and alsoaliphatic epoxy resins such as butane-1,4-diol diglycidyl ether orpolypropylene glycol-425 diglycidyl ether.

Examples of further suitable epoxides include cycloaliphaticbisepoxides, epoxidized polybutadienes formed by reacting commercialpolybutadiene oils with peracids or organic acid/H₂O₂ mixtures,epoxidation products of naturally occurring fats or oils, and suitableacrylate resins containing independent oxirane groups.

Particularly suitable alcohols for the polyaddition with epoxides arethe diols (b) used for the preparation of the polyurethanes.

As amines for the polyaddition with epoxides it is possible inparticular to use compounds containing at least two amine functions,examples being isophoronediamine, N-(2-hydroxyethyl)-1,3-propanediamineor else 3,3′-dimethyl-4,4-diaminodicyclohexylmethane.

As polyadducts with epoxides it is additionally possible to make use inparticular of compounds with two acid anhydrides or with two carboxylicacids, for example, maleic acid and maleic anhydride, azelaic acid anddodecanoic acid, or else norcaranedicarboxylic acid or dimer fatty acidsor cyclohexanedicarboxylic acids.

In the case of the polyadducts with epoxides, the ratio of theirconstituent monomers, i.e., the epoxide compounds on the one hand andthe alcohols, amines, carboxylic acids and/or acid anhydrides on theother, is situated in a range such that the ratio of epoxide functionson the one hand and epoxide-reactive functions on the other is from0.2:1 to 5:1, in particular from 0.5:1 to 2:1, preferably from 0.8:1 to1.2:1 and with particular preference 1:1.

The proportion of the polyadducts, based on the sum of the fractions ofthe polyadducts and of the free-radical addition polymers, is preferablyfrom 1 to 99% by weight, in particular from 5 to 95% by weight, and withparticular preference from 10 to 90% by weight.

The polyaddition reaction is preferably conducted at temperatures from30 to 120° C., in particular at from 40 to 100° C. It is generallyinitiated by an increase in temperature. It may also be advisable tooperate under superatmospheric pressure.

Suitable free-radical addition polymers are all polymers which can beobtained by free-radical addition polymerization from the correspondingfree-radically polymerizable monomers. The free-radical additionpolymerization is conducted in particular at temperatures from 20 to150° C., with particular preference at temperatures from 40 to 120° C.The polymerization may also take place under superatmospheric pressureand be carried out with induction by radiation, in particular UVradiation.

Preferably at least 40% by weight, with particular preference at least60% by weight, of the free-radical addition polymer is composed of whatare termed principal monomers, selected from C₁-C₂₀ alkyl(meth)acrylates, C₃-C₂₀ cycloalkyl (meth)acrylates, vinyl esters ofcarboxylic acids containing up to 20 carbon atoms, vinylaromatics havingup to 20 carbon atoms, ethylenically unsaturated nitriles, vinylhalides, vinyl ethers of alcohols containing 1 to 10 carbon atoms,aliphatic hydrocarbons having 2 to 8 carbon atoms and 1 or 2 doublebonds, or mixtures of these monomers.

Examples include (meth)acrylic acid alkyl esters having a C₁-C₁₀ alkylradical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate,ethyl acrylate, and 2-ethylhexyl acrylate.

Also suitable in particular are mixtures of the (meth)acrylic acid alkylesters.

Vinyl esters of carboxylic acids having 1 to 20 carbon atoms are, forexample, vinyl laurate, vinyl stearate, vinyl propionate, Versatic acidvinyl esters, and vinyl acetate.

Suitable vinylaromatic compounds include vinyltoluene, α- andp-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene andpreferably styrene.

Examples of nitriles are acrylonitrile and methacrylonitrile.

The vinyl halides are ethylenically unsaturated compounds substituted bychlorine, fluorine or bromine, preferably vinyl chloride and vinylidenechloride.

Examples of vinyl ethers include vinyl methyl ether and vinyl isobutylether. Preference is given to vinyl ethers of alcohols containing 1 to 4carbon atoms.

As hydrocarbons having 2 to 8 carbon atoms and two olefinic double bondsmention may be made of butadiene, isoprene and chloroprene; examples ofthose having one double bond include ethene and propene.

In addition to these principal monomers, the addition polymer maycontain further monomers, e.g., hydroxyl-containing monomers, especiallyC₁-C₁₀ hydroxyalkyl (meth)acrylates, C₃-C₂₀ hydroxy(cyclo)alkyl(meth)acrylates, (meth)acrylamide, ethylenically unsaturated acids,especially carboxylic acids, such as (meth)acrylic acid or itaconicacid, and their anhydrides, dicarboxylic acids and their anhydrides ormonoesters, e.g., maleic acid, fumaric acid, and maleic anhydride. Veryparticular preference is given to C₁-C₁₀ hydroxyalkyl (meth)acrylates.

The hybrid dispersions of the invention comprising the polyadducts andthe free-radical addition polymers are preferably obtainable byconducting the polyaddition and free-radical addition polymerization inan aqueous miniemulsion whose monomer droplets have a particle size ofnot more than 1000 nm, preferably not more than 500 nm, in particularnot more than 300 nm. With particular preference the particle sizes ofthe monomer droplets in the case of a miniemulsion are from 50 to 300nm. The fine dispersion of the monomer droplets in the case of aminiemulsion is accomplished by mechanical introduction of energy in theform, for example, of strong shearing. Such shearing may take place,inter alia, by means of two opposingly directed nozzles in a mixingchamber. A further possibility is to carry out shearing usingultrasound, by means of an ultrasound rod, for example, or using anozzle jet disperser.

In the case of a miniemulsion it is possible to add what is termed acostabilizer to the monomers, said costabilizer featuring low solubilityin water and high solubility in the monomers.

In miniemulsion polymerization, the addition polymerization orpolyaddition takes place in the monomer droplets themselves.

The hybrid dispersions of the invention are obtainable by emulsifyingthe constituent monomers of the polyadducts and free-radical additionpolymers in water and conducting the polyaddition reaction and/orfree-radical addition polymerization in the resulting emulsion. Theaqueous emulsion is normally built with the aid of suitable emulsifiersand/or protective colloids or stabilizers. It is also possible toemulsify only some of the monomers in water and-to add the remainderlater in the course of the reaction, preferably by way of the aqueousphase.

In the case of emulsion polymerization it is general practice to useionic and/or nonionic emulsifiers and/or protective colloids orstabilizers as surface-active compounds.

An in-depth description of suitable protective colloids is given inHouben-Weyl, Methoden der organischen Chemie, volume XIV/1,Makromolekulare Stoffe, Georg-Thieme-Verlag, Stuttgart, 1961, pp. 411 to420. Suitable emulsifiers include anionic, cationic, and nonionicemulsifiers. As accompanying surface-active substances it is preferredto use exclusively emulsifiers, whose molecular weights, unlike those ofthe protective colloids, are usually below 2000 g/mol. Where mixtures ofsurface-active substances are used the individual components must ofcourse be compatible with one another, something which in case of doubtcan be checked by means of a few preliminary tests. It is preferred touse anionic and nonionic emulsifiers as surface-active substances.Examples of common accompanying emulsifiers include ethoxylated fattyalcohols (EO units: 3 to 50, alkyl: C₈ to C₃₆), ethoxylated mono-, di-,and tri-alkylphenols (EO units: 3 to 50, alkyl: C₄ to C₉), alkali metalsalts of dialkyl esters of sulfosuccinic acid, and alkali metal saltsand ammonium salts of alkyl sulfates (alkyl: C₈ to C₁₂), of ethoxylatedalkanols (EO units: 4 to 30, alkyl: C₁₂ to C₁₈), of ethoxylatedalkylphenols (EO units: 3 to 50, alkyl: C₄ to C₉), of alkylsulfonicacids (alkyl: C₁₂ to C₁₈), and of alkylarylsulfonic acids (alkyl: C₉ toC₁₈).

Suitable emulsifiers are also given in Houben-Weyl, Methoden derorganischen Chemie, volume 14/1, Makromolekulare Stoffe, Georg ThiemeVerlag, Stuttgart, 1961, pages 192 to 208.

Tradenames of emulsifiers include, for example, Dowfax® 2 A1, Emulan® NP50, Dextrol® OC 50, Emulgator 825, Emulgator 825 S, Emulan® OG, Texapon®NSO, Nekanil® 904 S, Lumiten® I-RA, Lumiten E 3065 etc.

The surface-active substance is commonly used in amounts of from 0.1 to10% by weight, based on all the monomers to be polymerized.

Water-soluble initiators for the free-radical emulsion polymerizationare, for example, ammonium salts and alkali metal salts ofperoxodisulfuric acid, e.g., sodium peroxodisulfate, hydrogen peroxideor organic peroxides, e.g., tert-butyl hydroperoxide.

Particularly suitable are the systems known as reduction-oxidation(redox) initiator systems.

The redox initiator systems are composed of at least one, usuallyinorganic, reducing agent and one organic or inorganic oxidizing agent.

The oxidizing component comprises, for example, the initiators alreadymentioned above for the emulsion polymerization.

The reducing components comprise, for example, alkali metal salts ofsulfurous acid, such as sodium sulfite, sodium hydrogensulfite, alkalimetal salts of disulfurous acid such as sodium disulfite, bisulfiteaddition compounds with aliphatic aldehydes and ketones, such as acetonebisulfite, or reducing agents such as hydroxymethanesulfinic acid andits salts, or ascorbic acid. The redox initiator systems may be usedtogether with soluble metal compounds whose metallic component is ableto exist in a plurality of valence states.

Common redox initiator systems include, for example, ascorbicacid/iron(II) sulfate/sodium peroxodisulfate, tert-butylhydroperoxide/sodium disulfite, and tert-butyl hydroperoxide/Nahydroxymethanesulfinate. The individual components, the reducingcomponent for example, may also be mixtures, one example being a mixtureof the sodium salt of hydroxymethanesulfinic acid with sodium disulfite.

Said compounds are generally used in the form of aqueous solutions, thelower concentration being determined by the amount of water that isacceptable in the dispersion and the upper concentration by thesolubility of the respective compound in water.

The concentration is generally from 0.1 to 30% by weight, preferablyfrom 0.5 to 2.0% by weight, with particular preference from 1.0 to 10%by weight, based.on the solution.

The amount of the initiators is generally from 0.1 to 10% by weight,preferably from 0.2 to 5% by weight, based on all the monomers to bepolymerized. It is also possible to use two or more different initiatorsfor the emulsion polymerization.

The polymerization medium for the emulsion may be composed either ofwater alone or of mixtures of water and water-miscible liquids such asacetone. It is preferred to use just water. The hybrid dispersions canbe prepared in a batch operation or else as a feed process, or else as acontinuous process.

The manner in which the initiator is added to the polymerization vesselin the course of the free-radical aqueous emulsion polymerization isfamiliar to the skilled worker. It may either all be included in theinitial charge to the polymerization vessel or else added, continuouslyor in stages, at the rate at which it is consumed in the course of thefree-radical aqueous emulsion polymerization. Specifically this willdepend, in a manner familiar to the skilled worker, both on the chemicalnature of the initiator system and on the polymerization temperature.Preferably, one portion is included in the initial charge and theremainder is supplied to the polymerization zone at the rate at which itis consumed.

The process, likewise of the invention, for preparing the hybriddispersions of the invention, comprises first emulsifying theconstituent monomers of the polyadducts and the free-radical additionpolymers in water and then conducting the polyaddition to prepare thepolyadducts and the free-radical addition polymerization to prepare thefree-radical addition polymers, the respective monomers being emulsifiedin water before 40% of the monomers of which the polyadducts arecomposed have reacted to form such polyadducts.

The process of the invention can be carried out by conducting thepolyaddition and the free-radical addition polymerization at the sametime. A further possibility, accomplished for example by raising thetemperature, is to conduct the polyaddition first and then, by additionof initiators, for example, to run the free-radical additionpolymerization. Conversely it is likewise possible first to conduct thefree-radical addition polymerization and thereafter the polyaddition.Both the polyaddition and the free-radical addition polymerization takeplace with retention of the particle size from the emulsifying step.

Both reactions, i.e., the polyaddition and the free-radical additionpolymerization, may take place alongside one another without disruption,so giving two polymers independent of one another. Through anappropriate choice of the monomers employed, however, it is alsopossible to prepare the corresponding copolymers. Furthermore, by dintof suitable reaction conditions, graft copolymers may also be formed.If, in addition, use is made of polyfunctional monomers, then theproducts include semiinterpenetrating networks or crosslinkedstructures.

Suitable reactors for conducting the process of the invention forpreparing the hybrid dispersions include the apparatus customary inpolymerization art, preference being given to the use of stirred tanksespecially when effective heat removal is important.

The hybrid dispersions of the invention are suitable in particular asbinders for the coating compositions or impregnating compositions, e.g.,for adhesives, varnishes, paints or paper coating slips, or as bindersfor fiber webs; in other words, anywhere where crosslinking and anincrease in internal strength (cohesion) are desired.

Depending on the intended use, the aqueous dispersion may compriseadditives such as thickeners, leveling assistants, pigments or fillers,fungicides, light stabilizers, wetting agents, rheological aids,defoamers, tack additives or corrosion protection additives. Theseadditives may also be present in the monomer droplets, directly.

When used as adhesives, the dispersions may include specific auxiliariesand additaments common in adhesive technology, as well as the additivesreferred to above. Said auxiliaries and additaments include, forexample, thickeners, plasticizers or else tackifying resins such as, forexample, natural resins or modified resins such as rosin esters orsynthetic resins such as phthalate resins.

The hybrid dispersions of the invention are distinguished by a particlesize distribution which is not too broad, and may include a very largenumber of different adducts and free-radical addition polymers.Surprisingly it has also been found that, inter alia, very finelydivided polyacrylates and polystyrenes may also be present together withhigh fractions of polyurethanes in the hybrid dispersions of theinvention. The hybrid dispersions are obtainable by a relatively simpleprocess which is likewise part of the invention.

EXAMPLES Example 1

A mixture of 1.578 g of isophorone diisocyanate, 1.429 g ofdodecanediol, 3 g of styrene and 250 mg of hexadecane was added to 24 gof water containing 180 mg of sodium dodecyl sulfate. The mixture wasmixed for an hour at the highest magnetic stirrer setting. An ultrasoundrod (Branson Sonifier W450, 90% amplitude for 2 minutes) was used toprepare the stable miniemulsion. The miniemulsion was heated to 60° C.After 4 hours, 60 mg of potassium peroxodisulfate were added to thesystem and the temperature was raised to 72° C. in order to initiate thefree-radical addition polymerization. Complete monomer conversion isachieved after 3 hours. The particle size is 92 nm. Investigation byinfrared spectroscopy shows the conversion of the isocyanate groups,while gravimetry demonstrates that the styrene has been converted. Inthe GPC, two separate peaks are found. By means of transmission electronmicroscopy, a homogeneous particle morphology is detected.

Example 2

Like Example 1 but using polytetrahydrofuran 1000 instead ofdodecanediol. The particle size is 101 nm.

Example 3

Like Example 1 but using butyl acrylate instead of styrene. The particlesize is 98 nm.

Example 4

A mixture of 1.57 g of isophorone diisocyanate (IPDI), 1.3 g ofdodecanediol, 185 mg of hydroxybutyl acrylate, 3 g of butyl acrylate and250 mg of hexadecane was added to 24 g of water containing 180 mg ofsodium dodecyl sulfate. The mixture was mixed for an hour at the highestmagnetic stirrer setting. An ultrasound rod (Branson Sonifier W450, 90%amplitude for 2 minutes) was used to prepare the stable miniemulsion.The miniemulsion was heated to 60° C. After 4 hours, 60 mg of potassiumperoxodisulfate were added to the system and the temperature was raisedto 72° C. in order to initiate the free-radical addition polymerization.Complete monomer conversion is achieved after 3 hours. The particle sizeis 103 nm. Investigation by infrared spectroscopy shows the conversionof the isocyanate groups, while gravimetry demonstrates that theacrylates have been converted. The resulting polymer is insoluble andonly swells in chloroform or DMF.

Example 5

Like Example 4 but the monomer mixture is changed in order to achievehigher levels of crosslinking. Hydroxybutyl IPDI Dodecanediol acrylateParticle size 1.57 g 1.30 g 185 mg 103 nm 1.57 g 1.19 g 340 mg  93 nm1.57 g 0.95 g 680 mg 110 nm

1. A hybrid dispersion comprising polyadducts and free-radical additionpolymers, obtainable by first emulsifying the constituent monomers ofsaid polyadducts and polymers in water and then conducting thepolyaddition to prepare the polyadducts and the free-radical additionpolymerization to prepare the polymers, the respective monomers beingemulsified in water before 40% of the monomers of which the polyadductsare composed have reacted to form such polyadducts.
 2. The hybriddispersion as claimed in claim 1, obtainable by conducting thepolyaddition and the free-radical addition polymerization in an aqueousminiemulsion whose monomer droplets have a monomer particle size of notmore than 1000 nm.
 3. The hybrid dispersion as claimed in claim 1,obtainable by emulsifying the respective monomers in water before 20% ofthe monomers of which the polyadducts are composed have reacted to formsuch polyadducts.
 4. The hybrid dispersion as claimed in claim 1,obtainable by emulsifying the respective monomers in water before 5% ofthe monomers of which the polyadducts are composed have reacted to formsuch polyadducts.
 5. The hybrid dispersion as claimed in claim 1,comprising polyurethanes and polyurethaneureas as polyadducts.
 6. Thehybrid dispersion as claimed in claim 1, comprising polyadducts formedby reaction of epoxide groups with alcohols, acids, amines oranhydrides.
 7. The hybrid dispersion as claimed in claim 1, comprisingfree-radical addition polymers composed in total of at least 40% byweight of principal monomers selected from C₁ to C₂₀ alkyl(meth)acrylates, C₃ to C₂₀ cycloalkyl (meth)acrylates, vinylaromaticshaving up to 20 carbon atoms, vinyl esters of carboxylic acids having 1to 20 carbon atoms, ethylenically unsaturated nitrites, vinyl ethers ofalcohols containing 1 to 10 carbon atoms, vinyl halides, nonaromatichydrocarbons having 2 to 8 carbon atoms and one or two conjugated doublebonds, and mixtures of these monomers.
 8. The hybrid dispersion asclaimed in claim 1, the proportion of the polyadducts based on the sumof the fractions of the polyadducts and of the free-radical additionpolymers being from 1 to 99% by weight.
 9. A process for preparing ahybrid dispersion comprising polyadducts and free-radical additionpolymers, which comprises first emulsifying the constituent monomers ofsaid polyadducts and polymers in water and then conducting thepolyaddition to prepare the polyadducts and the free-radical additionpolymerization to prepare the polymers, the respective monomers beingemulsified in water before 40% of the monomers of which the polyadductsare composed have reacted to form such polyadducts.
 10. The process asclaimed in claim 9, wherein the polyaddition and the free-radicaladdition polymerization are conducted at the same time.
 11. The processas claimed in claim 9, wherein first the polyaddition and then thefree-radical addition polymerization is conducted.
 12. The process asclaimed in claim 9, wherein first the free-radical additionpolymerization and then the polyaddition is conducted.
 13. The processas claimed in claim 9, conducted in a miniemulsion generated by means ofultrasound or by means of a nozzle jet emulsifier.
 14. The process asclaimed in claim 9, wherein the free-radical addition polymerization isconducted at temperatures of from 20 to 150° C.
 15. The process asclaimed in claim 9, wherein the polyaddition is conducted attemperatures from 30 to 120° C.
 16. The process as claimed in claim 9,wherein the free-radical addition polymerization or the polyaddition isperformed under superatmospheric pressure.
 17. The process as claimed inclaim 9, wherein the addition polymerization is conducted with inductionby radiation.
 18. A binder for coating compositions or impregnatingcompositions comprising the hybrid dispersion as claimed in claim
 1. 19.A binder in adhesives, varnishes, paints, paper coating slips or fiberwebs comprising the hybrid dispersion as claimed in claim
 1. 20. Amethod for binding a material comprising utilizing the hybrid dispersionas claimed in claim 1 as a binder.
 21. The method for binding a materialas claimed in claim 20 wherein said material is at least one selectedfrom the group consisting of a coating composition, an impregnatingcomposition, an adhesive, a varnish, a paint, a paper coating slip and afiber web.